Electronic systems, particularly those used on aircraft, require weight and volume efficiency. The efficiency of an aircraft is a function of the payload which the aircraft can carry for the available thrust. Payload is most often measured in terms of revenue generating weight. That is, the more revenue generating weight that an aircraft can carry for the available thrust, the more efficient the aircraft becomes. Ideally, the ratio of payload (i.e. the revenue generating weight) to aircraft weight (i.e. the weight of the aircraft itself without payload) can be maximized by reducing aircraft weight. Aircraft weight and volume can be reduced, in turn, by reducing the weight and volume of the components which are part of the air frame structure. These components include not only the structural elements of the air frame but also the aircraft's electronics.
There are many electronic systems on an aircraft for providing a variety of tasks such as power generation and regulation, communications, and control of air surfaces. These electronic systems typically generate, and are susceptible to, electromagnetic interference. As a result, such electronic systems rely extensively upon filtering. For example, filters are used in an aircraft's electronic systems for filtering out undesired harmonics, for transient suppression, and for a variety of other tasks all generally related to reducing or eliminating undesired signals on the electrical transmission paths of the these electronic systems.
These filters include, inter alia, differential mode filters for filtering out undesired signals which are conducted on one transmission path relative to another path, common mode filters for filtering out undesired signals being conducted on two or more transmission paths (typically where such signals change simultaneously and by the same amount relative to some common reference such as ground), and mixed mode filters for filtering out both undesired differential mode and undesired common mode signals. Such filters are typically constructed discretely by winding wire on a ferromagnetic core to form inductors and connecting the inductors in series with capacitors. This type of construction results in undesirably large and heavy filter components for electronic systems.